Air compressor assembly

ABSTRACT

An air compressor with a cylinder head attached to a cylinder deck of a crankcase is disclosed. Openings are provided through the cylinder deck and cylinder head and elongated fasteners having a fastening complement are used to provide a compressed engagement between the deck and cylinder head. Using a fastener inserted through the openings and a fastener complement reduces the potential that the bore is distorted during assembly without adding material to the assembly that undesirably increases its weight or complicates foundry operations. Machining of the deck is also simplified by providing the opening therethrough.

BACKGROUND OF THE INVENTION

[0001] This application relates to a compressor assembly, and more particularly, to an air compressor, such as one that provides and maintains air under pressure for operating air brakes and/or associated air-operated auxiliary systems associated with heavy vehicles.

[0002] Conventional air compressor assemblies having a cylinder head and a crankcase are assembled with threaded fasteners or bolts that pass through openings in the cylinder head into blind end threaded openings in a cylinder deck of the crankcase to which the cylinder head is attached. The openings in the cylinder head are aligned with the threaded openings in the cylinder deck to allow the fasteners to pass through the cylinder head into the cylinder deck. Typically, there are four or six such sets of openings, spaced around the cylinder head and the cylinder deck. A typical assembly is shown in FIG. 3.

[0003] As the assembly is drawn together by tightening the fasteners, the potential exists that bores within cylinders in the crankcase will become distorted by, among other causes, uneven application of tightening forces to the fasteners spaced around the assembly. Bore distortion could adversely affect the operation of the air compressor by impacting sealing arrangements of cylinders within the bores, resulting in increased leakage of oil from the compressor assembly. Such increased leakage could contaminate downstream components in a compressed air system and could cause environmental concerns.

[0004] Distortion of compressor components is a known problem, as discussed in U.S. Pat. No. 4,530,323. As therein discussed, elongated threaded fasteners pass through openings in the cylinder head and are threadedly received in recesses of a cylinder block. The problem addressed therein, however, relates to distortion in the cylinder head and provision of reinforcing ribs is taught to address that problem.

[0005] Similarly, U.S. Pat. No. 5,630,389 is concerned with flexing and potential cracking of the cylinder head upon tightening of fasteners used to secure the cylinder head to an engine block. The solution proposed in that patent is to situate the fasteners closer to the engine block, thereby reducing flexing of the cylinder head and associated potential cracking of the cylinder head.

[0006] U.S. Pat. No. 5,873,331 is also concerned with even distribution of clamping forces from a cylinder head to an engine block. The proposed solution taught therein is to orient bolt receiving columns in a particular manner and thereby more uniformly distribute bolt forces and thus reduce assembly distortions.

[0007] Still another proposed solution offered by U.S. Pat. No. 6,016,783 is to provide an induction hardened cylinder head with selected surfaces areas contacted by heads of fastener bolts.

[0008] In the field of internal combustion engines, U.S. Pat. No. 5,072,697 discloses use of aligned bolt holes in the cylinder head and block, and retention of the bolts through use of fastener nuts. A similar arrangement is illustrated in a plastic composite construction for an internal combustion engine in U.S. Pat. No. 4,848,292.

SUMMARY OF THE INVENTION

[0009] The present invention provides an air compressor assembly that reduces cylinder bore distortion without adding material to the cylinder deck, which would increase the weight and the rigidity of the assembly. The present invention also provides a method of reducing bore distortions in an air compressor in a simple, economical manner.

[0010] The air compressor assembly of the present invention includes a crankcase having at least one cylinder formed therein that receives a piston for compressing air. A cylinder head is secured to the crankcase. The cylinder head and a portion of the crankcase, herein identified as the cylinder deck, include aligned openings that freely receive fasteners therethrough. The fasteners are threaded along one end and secured by a fastening nut.

[0011] A method of reducing bore distortions in an air compressor is also disclosed that includes providing a crankcase with at least one cylinder bore, supplying a cylinder head for attachment to a crankcase, forming openings in the cylinder head and crankcase without any threads, and inserting fasteners through the openings.

[0012] The present invention provides reduction of bore distortion in the crankcase, improved sealing characteristics about the piston, reduced adverse impact on the environment, simplified machining of the cylinder deck or crankcase, and does not add material or weight to the assembly.

[0013] Still other features of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention may take physical form in certain parts and arrangements of parts, an embodiment of which is described in detail in this specification and illustrated in the accompanying drawings.

[0015]FIG. 1 is an exploded perspective view of a cylinder head and crankcase for an air compressor.

[0016]FIG. 2 is a longitudinal cross-section through a conventional compressor.

[0017]FIG. 3 is an enlarged cross-sectional view of prior art attachment of the cylinder head to the crankcase.

[0018]FIG. 4 is an elevational view of a compressor in accordance with the present invention, shown partly in section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019]FIG. 1 illustrates a conventional air compressor assembly. The compressor assembly includes a body or crankcase 10 and a cylinder head 20. The crankcase 10 includes an upper, terminal portion having a planar surface, identified as cylinder deck 22. First and second cylinder bores 24 are formed in the crankcase 10 and each bore 24 houses a piston 26, as shown in FIG. 2, to pressurize air in chamber 30 located above the piston 26 for an associated compressed air system or other use (not shown). Each piston 26 has seal rings 28 along a peripheral portion thereof and is driven via connecting rod 32 that is secured to a crankshaft 34 to convert the rotary input drive (not shown) into reciprocating movement of the piston 26. Further details of the structure and operation of the air compressor assembly are generally conventional and may be of any suitable conventional design.

[0020]FIG. 1 illustrates that the cylinder head 20 sealingly engages or mates with the cylinder deck 22 along a planar interface. A gasket 40, such as a metallic or graphite gasket, may be interposed between the cylinder head 20 and the cylinder deck 22. The gasket 40 includes enlarged openings 42 that accommodate passage of air from the respective cylinder bores 24. In addition, smaller openings 44 are spaced along the periphery of the gasket 40. The smaller openings 44 are dimensioned and positioned for alignment with associated openings 50 in the cylinder deck of the crankcase.

[0021] In addition, openings 52 are provided in the cylinder head 20 and are likewise dimensioned and positioned for alignment with the respective openings 44 in the gasket 40 and openings 50 formed in the cylinder deck 22. The openings 52 have a smooth bore, without threads. Fasteners 54, such as elongated threaded bolts, are dimensioned for receipt through the aligned openings 52, 44, 50 of the cylinder head 20, gasket 40, and cylinder deck 22, respectively. Each fastener has an enlarged head portion 56 at one end and is preferably threaded at a second end 58.

[0022]FIG. 3 illustrates conventional attachment of the cylinder head 20 to the crankcase 10, wherein like components are referenced by like numerals with a primed (′) suffix. Thus, cylinder head 20′ includes openings 52′ therethrough at predetermined locations. The crankcase 10′ includes a cylinder deck 22′ having mounting recesses 60 that are blind-end recesses and internally threaded. Stated another way, the individual fasteners 54′ are dimensioned for threaded engagement with the internal threads of the recess 60. The head portion 56′ has a dimension larger than the opening 52′ in the cylinder head. In this manner, when threaded ends 58′ of the fastener 54′ engage with the threaded recess 60 in the cylinder deck 22′, the cylinder head 20′ compressingly engages the cylinder deck 22′ and gasket (not shown in FIG. 3). This provides a desired seal engagement between the cylinder head 20′ and the crankcase 10′ of the compressor assembly that allows the compressed air to be transferred in a pressurized state for downstream use such as air braking, etc.

[0023] Cylinder bores 24, as illustrated in FIG. 1, may be adversely affected by this mounting arrangement, because additional stresses arising during formation of the threaded recesses 60 and assembly of the cylinder head 20 and crankcase 10 can result in undesirable distortion of the cylinder bores 24. Distortion of the bores 24 results in less than optimal sealing of the piston seal rings 28, as shown in FIG. 2, with the cylinder wall and thereby presents the potential that oil bypasses the rings 28 and is introduced into the compressed air in chamber 30. Eliminating distortions in the bore 24 improves the overall quality of the compressed air system, by reducing passage of oil to the chamber 30 and entrainment of oil in the compressed air system.

[0024] One embodiment of the invention is illustrated in FIG. 4. Openings 50 provided in the cylinder deck 22 of the crankcase 10 illustrated in FIG. 1 are dimensioned to freely receive the elongated fasteners 54 therethrough. This is in contrast to the mounting recesses 60 used in the conventional arrangement of FIG. 3. In addition, the internal threading necessary for the mounting recesses 60 is removed, which eliminates another machining step and the potential for distortion that can arise therewith. Thus, the openings 50 are of smooth bore, without threads. The fasteners 54 are slightly elongated and the second end 58 cooperates with fastener complements 70. Fastener complements 70 may be any device that prevents the fastener 54 from being inadvertently withdrawn, and includes nuts, cotter pins, clips, or the like.

[0025] In a preferred embodiment, the cylinder deck 22 and the cylinder head 20 are substantially rectangular, in which case it is desirable that there be at least four fasteners 54 located at corners of the cylinder deck 22 that are mounted in this manner. Other shapes mounting arrangements, such as six fasteners 54 as illustrated in FIG. 1, or two fasteners 54, or eight fasteners 54, may be used without departing from the spirit and scope of the invention. The choice and arrangement of the fasteners 54 and associated openings 52, 44, 50 are within the discretion of the user, depending on cost, materials, and other considerations.

[0026] In this manner, the cylinder head 20 still compressingly engages the cylinder deck 22 through the clamping force imparted by the fasteners 54. Here, however the fastener head 56 and the associated fastener complement 70 place the fastener 54 in a tension state that clampingly engages the cylinder head 20 to the crankcase 10 while limiting the prospect for distortion to arise. Simplified machining of the components is achieved and bore distortions are addressed without adding material or undesirable weight or increased rigidity to the crankcase 10.

[0027] The invention has been described with reference to a preferred embodiment. Modifications and alterations may occur to others upon reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims of the equivalents thereof. 

Having thus described the invention, it is claimed:
 1. An air compressor assembly comprising; a crankcase having at least one cylinder formed therein and a cylinder deck with first fastener receiving openings therethrough, the at least one cylinder capable of receiving a piston; and a cylinder head secured to the cylinder deck, the cylinder head including second fastener receiving openings therethrough spaced for alignment with the first fastener receiving openings.
 2. The air compressor assembly of claim 1, wherein the first and the second fastener receiver openings have a smooth bore.
 3. The air compressor assembly of claim 1, further comprising fasteners disposed through the first and second fastener receiving openings.
 4. The air compressor assembly of claim 3 wherein the fasteners are bolts threaded along at least one end and an associated nut.
 5. The air compressor assembly of claim 4 wherein the fastener nuts have a dimension greater than the first fastener receiving openings for abutting engagement with an underside thereof.
 6. The air compressor assembly of claim 1 further comprising a gasket interposed between the cylinder deck and the cylinder head.
 7. The air compressor assembly of claim 1 wherein the cylinder head has a substantially rectangular conformation and the fastener receiving openings are located at corner regions thereof.
 8. An air compressor assembly comprising: a crankcase with at least one cylinder bore formed therein and having a cylinder deck with first fastener receiving openings therethrough; a cylinder head having second fastener receiving openings therethrough at locations aligned with the first fastener receiving openings; and fasteners having a head at a first end and threads at a second end for receipt through the aligned openings in the deck and cylinder head, wherein the fastener heads abuttingly engage the cylinder head and nuts are threaded onto the fasteners and abuttingly engage the deck.
 9. The air compressor assembly of claim 8 further comprising a metal gasket interposed between the deck and cylinder head.
 10. A method for manufacturing an air compressor comprising: providing a crankcase with at least one cylinder bore formed therein; supplying a cylinder head for receipt on the crankcase; and forming aligned openings through the cylinder head and crankcase, the openings capable of receipt of fasteners therethrough.
 11. The method of claim 10, further comprising: inserting the fasteners through the openings; and securing the fasteners externally of the openings to attach the cylinder head to the crankcase.
 12. The method of claim 11 wherein the fasteners comprise a bolt threaded at one end.
 13. The method of claim 12 wherein the securing step comprises threading a nut onto the threaded end of the bolt. 